Is there a way to open a second firefox instance using a shortcut key (i.e. Ctrl + Alt + 9), while a first instance is already running?
This happens both in Windows XP and Windows 7. Firefox is the only application that does not allow this consistently (this works with MS-Word, Google Chrome, Notepad etc.).
Opaite Mbohovái (3)
Technically speaking, Firefox will only run one "instance".
Have you tried using {Ctrl + N} to open a new Firefox window??
Yes, but {Ctrl + N} is useful only when you are already in Firefox. I meant quickly launching Firefox while using another application via a user-assigned shortcut key. For example, I am writing a text in MS-Word and I want to run a quick Wikipedia search; now, if Firefox is already running in the background, my shortcut for Firefox (e.g Ctrl + Alt + 9) won't do anything - it will only launch Firefox, if it is the first Firefox window to be opened. Thanks anyway though!